A Washington University in St. Louis team has developed a catalyst that can be used to both generate fuel and provide power.

A single device that both generates hydrogen fuel and oxidant from water and, when a switch is flipped, converts the fuel and oxygen into electricity and water, has a host of benefits for terrestrial, space and military applications. From low environmental impact to high energy density, developing efficient unitized regenerative fuel cells, or URFCs as they are called, have been in researchers’ sights for years now.

But to truly be efficient, an URFC needs bifunctional catalysts. This means, in electrolyzer mode, catalysts should facilitate the breakdown of water into hydrogen and oxygen, and, in fuel cell mode, facilitate their recombination into water.

Bifunction Graphic shows the pathways of the raw material water, the products and the power system. Image Credit: Washington University St Louis. Click image for the largest view.

Now, working in the lab of Vijay Ramani, the Roma B. & Raymond H. Wittcoff Distinguished University Professor, a team of researchers has found an excellent bifunctional catalyst for the oxygen electrode. Their work has been published in the journal Proceedings of the National Academy of Sciences.

Pralay Gayen, currently working at Intel, who was a postdoctoral research associate in Ramani’s lab at the McKelvey School of Engineering at Washington University in St. Louis and served as the paper’s first author said, “Unlike the hydrogen electrode, wherein platinum is an effective bifunctional catalyst, it is very challenging to identify a suitable catalyst for the oxygen electrode due to the sluggish kinetics of oxygen reduction and oxygen evolution.”

Sulay Saha, a postdoctoral research associate in Ramani’s laboratory, and Gayen’s research was guided by first principles – taking into account the fundamental properties of different substances before heading to the lab to test potential catalysts.

Along with former undergraduate researcher and co-author Xinquan Liu, the team ultimately identified and developed Pt-Pyrochlore, a composite of platinum and a lead ruthenate pyrochlore, which yielded high bifunctionality.

The “bifunctionality index” is a measure of catalyst’s ability to facilitate both the forward and reverse direction of a reaction. “We want the index to be low,” said Kritika Sharma, a PhD engineering student. “Zero, ideally.” This new catalyst has a bifunctionality index of 0.56 volts – very low compared with other catalysts reported. When used in a URFC device developed by the laboratory, the catalyst enabled a round-trip energy efficiency (RTE) of 75% – the highest reported round-trip efficiency in this type of URFC.

With such high efficiency, the URFCs developed are well suited for applications such as submersibles, drones, spacecrafts and space stations, as well as for off-grid energy storage.


This team has achieved some remarkable numbers in the lab tests. They have come a long way in leading to a solution for the oxygen side of the process. Congratulations are in order for the power of their intellect. Only one big problem remains, the rarity and cost of platinum.


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